President Trump's former campaign manager, Paul Manafort, and Manafort's ex-business associate, Rick Gates, have pleaded not guilty during their arraignments on federal charges related to a government investigation into Russian meddling in the U.S. election.

The 12-count indictments brought Monday against Manafort and Gates include charges of conspiracy against the United States, conspiracy to launder money, giving false and misleading statements to federal officials and failure to file reports on foreign bank and financial accounts.

The charges do not mention the Trump campaign, but instead detail the pair's alleged relationship with a political party in Ukraine.

The indictment alleges that between 2006 and 2015, Manafort and Gates laundered money through U.S. and foreign corporations, partnerships and bank accounts. More than $75 million passed through offshore accounts, according to the indictment.

The government sought a $10 million bond for Manafort and $5 million bail for Gates.

A third former Trump staffer, George Papadopoulos, pleaded guilty to making false statements to the FBI, the Justice Department announced.

Manafort enjoyed a "lavish lifestyle" using "hidden wealth" overseas but did not pay taxes on that money, the indictment said.

Manafort left his apartment in Alexandria, Va., Monday morning with his lawyer and made his way to the Washington office of the FBI to surrender.